The present invention relates in general to concrete and masonry construction, and, more particularly, to an apparatus and method for introducing pigments, colorants and other additives to the surface of plastic concrete.
Concrete can be molded into a variety of shapes and configurations including driveways, decks, concrete masonry units (CMU), blocks, beams, columns, decorative stones, mosaics and facades as examples of decorative concrete applications. Many of these products include a colorant or pigment which provides color to the application. Concrete additives such as plasticizers, pigments, colorants or dispersants are added to concrete mixes in order to increase the plasticity of the concrete, which improves the workability of the concrete prior to hardening. Color pigments may be added to concrete mix in order to produce a certain color for aesthetic enhancement of the concrete.
The addition of concrete pigment and other admixtures or additives to concrete mix is known in the art. For example, U.S. Pat. No. 7,270,469 discloses an apparatus and method for adding pigmentation to a concrete mix by using a pigmentation dispenser with a hopper and two rotors wherein the pigment is dispensed onto concrete mix traveling on a conveyor. The concrete mix and dispensed pigment are then conveyed to a mixer which mixes them together. However, such methods require the addition of pigment to the entire batch of concrete to be mixed resulting in a monolithic coloring of the entire concrete mixture, some of which will never be seen or viewed as certain of the concrete structure surfaces after finishing will face the ground or other structures and remain hidden from view. As a result, there is a certain waste volume of pigment generated in such mixing and coloring regimes. Likewise, if a deeper color is required, then the entire batch of colored concrete must be reintroduced to the coloring and mixing system again resulting in the additional waste of colorant to color then entire batch of concrete to be manipulated into a slab, façade, or CMU. Moreover, these methods of adding color hardeners or additives to a concrete mix or slab are performed prior to finishing or shaping of the concrete, thereby increasing the time required to complete the process or project.
The addition of color additives to cast in place concrete has traditionally been by hand. As a plastic concrete slab is being finished, a worker will take a handful of powderized color hardener and disperse it over the slab, in effect flinging a handful of dry color hardener powder into the air which disperses and falls by gravity on to the wet or plastic concrete surface. A color hardener is a powder that is applied to the surface of plastic, cast in place concrete. It colors the concrete and acts to “harden” the concrete slab.
This method of color hardener application has serious drawbacks. For example, the color hardener powder is dispersed erratically in an uncontrolled amount and in variable concentration on to the concrete slab, which can result in a non-uniform color. Depending on prevailing environmental conditions (e.g. wind), a substantial amount of the color hardener is dispersed and deposited on other surfaces close to the slab and goes to waste, as well as potentially bleeding color undesirably on other surfaces. A more serious drawback is that the powder may be inhaled by the worker and other workers on the site, potentially leading to detrimental physiological effects (sneezing, asthma or other undesirable health conditions). As a result, a need exists for an apparatus and method which effectively and safely broadcasts concrete color hardener or other additives on to a plastic cast in place slab.
Therefore, one object of the present invention is to provide an apparatus and method for the controlled dispensation and application of concrete colorants or additives to concrete surfaces without the need to monolithically mix such colorants or additives prior to finishing or manipulation of the concrete into the desired shape or structure.
A further object of the present invention is provide an apparatus and method which provides a mechanism by which pigments or other additives may be introduced to the concrete mixture in specific areas in the discretion of the operator as the concrete is being finished.
A further object of the present invention is the provision of an apparatus and method for introducing color hardener or other additives to concrete mix which is efficient in operation and conserves the volume of additive required to complete the concrete treatment process.